linux-kernel - Re: [PATCH 0/4] i386 - pte update optimizations

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Message-ID: <461FA2EE.5090103@zytor.com>
Date:	Fri, 13 Apr 2007 08:34:06 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Keir Fraser <keir@...source.com>
CC:	Andi Kleen <andi@...stfloor.org>, Zachary Amsden <zach@...are.com>,
	Andrew Morton <akpm@...l.org>,
	Virtualization Mailing List <virtualization@...ts.osdl.org>,
	Chris Wright <chrisw@...s-sol.org>,
	David Rientjes <rientjes@...gle.com>,
	Hugh Dickins <hugh@...itas.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/4] i386 - pte update optimizations

Keir Fraser wrote:
> On 13/4/07 13:27, "Andi Kleen" <andi@...stfloor.org> wrote:
> 
>>> LOCKed instruction suck really badly on the netburst microarchitecture (like
>>> factor of 10x, or not far off). I think it's probably because of their side
>>> effect of serialising memory accesses, causing horrible pipeline stalls.
>> Unfortunately they tend to be HyperThreaded usually (except for early ones
>> and Celerons) and need the LOCK anyways.
> 
> Fair point, although quite a few people disable HT.

Note we're talking a UP-only hack.

	-hpa
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